1. Field of the Invention
The present invention generally relates to subterranean wells and, more particularly, to the abandonment of wellheads for subterranean wells.
2. Relevant Background
A subterranean well includes a borehole drilled from surface to an underground formation layer from which oil and/or gas is produced. The well is cased to limit collapse of the borehole. For instance, a well is typically started with a relatively large hole that is cased with a so-called surface casing or conductor which is cemented in the borehole. The well is then continued with a smaller hole drilled to an intermediate depth and cased by an intermediate casing or casing string which extends to the surface. The upper end of the intermediate casing extends concentrically through the conductor and at least part of the intermediate casing is cemented in the borehole. The well is then continued with again a smaller hole drilled to the production zone and cased by production casing or a casing string which extends to the surface. The upper end of the production casing extends concentrically through the intermediate casing and at least part of the production casing is cemented in the borehole.
The upper ends of the intermediate casing and the production casing are suspended from a wellhead assembly which is supported on the surface casing. A conventional wellhead assembly includes a housing supported on the surface casing. The housing is provided with a central bore having internal support shoulders or the like. The wellhead assembly further includes casing hangers for suspending the intermediate casing and production casing from the internal support shoulders in the housing as well as a sealing arrangement for sealing off the annular spaces around the casing hangers.